fscache_begin_cache_access(9)

💖 fscache_begin_cache_access 💖

ok so this is the manual page for fscache_begin_cache_access(9) from the Kernel API Manual, and bestie, it's literally the "pin a cache so it can be accessed" function. let's get into it 🫶

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✨ SYNOPSIS ✨

bool fscache_begin_cache_access (struct fscache_cache *cache , enum
       fscache_access_trace why );

yeah that's the whole signature, no cap 💅

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🎀 ARGUMENTS 🎀

• cache — the cache-level cookie 🍪 (yes really, that's what it's called)
• why — an indication of the circumstances of the access, for tracing 🔍 like it's for the receipts, yk?

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🌸 DESCRIPTION 🌸

okay so the whole vibe here is: we attempt to pin the cache so it doesn't just dip while we're mid-access, and we return true if that worked out. it's giving "hold my spot bestie" 🤞

here's literally how it works, step by step, no skipping:

1. if the cache tests as not live (state is not FSCACHE_CACHE_IS_ACTIVE), then we return false to indicate access was not permitted 🙅‍♀️ like, door's closed, sorry babe.
2. if the cache tests as live, then we increment the n_accesses count and then recheck the liveness — ending the access if it ceased to be live 👀 (the double-check is so real of it)
3. when we end the access, we decrement n_accesses and wake up the any waiters if it reaches 0 💤➡️🔔
4. whilst the cache is caching, n_accesses is kept artificially incremented to prevent wakeups from happening 🧚✨ (it's fake it till you make it, but for counters)
5. when the cache is taken offline, the state is changed to prevent new accesses, n_accesses is decremented and we wait for n_accesses to become 0 ⏳ periodt.

lowkey important: steps 2 and 5 are the whole "pin so it doesn't go away mid-access" moment — if the liveness check fails you gotta end the access, no exceptions 👑

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🌈 SEE ALSO 🌈

• Kernel file ./fs/netfs/fscache_cache.c
• fscache_acquire_cache(9)
• fscache_put_cache(9)
• fscache_relinquish_cache(9)
• fscache_add_cache(9)
• fscache_end_cache_access(9)
• fscache_io_error(9)
• fscache_withdraw_cache(9)

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and that's the page babes 💜 this one's from ./fs/netfs, dated October 2026, sitting pretty in the Kernel API Manual as fscache_begin_cache_access(9) — iconic, no notes 🔥👑